This invention relates to the treatment of wastewater and more specifically to an aerobic wastewater treatment apparatus.
Wastewater treatment systems are known and can vary from large treatment plants to septic tanks used for on-site treatment.
Generally, most on-site septic tanks consist of a tank into which the wastewater is pumped. Organisms feed on the wastewater producing a mixture of mostly water, sludge and gases. The sludge will remain at the bottom of the tank while the water and gases are siphoned out of the tank. The water is usually filtered again prior to any subsequent use. The sludge accumulates in the tank and periodically needs to be removed and disposed of.
An alternative wastewater treatment system is the activated sludge method. This method uses a continuous flow of wastewater that flows into an aeration chamber in which organisms feed on the waste producing excess sludge, that generally requires further processing, and clarified water. This method produces large amounts of sludge that eventually needs to be disposed of and is quite sensitive to any change in the operating conditions that can subsequently affect the microbial population. Alternatives to this type of system have been proposed, for example in U.S. Pat. No. 5,582,732 (Mao et al.) a method is described that uses a special acclimatized microbial consortia that are less susceptible to changes in operating conditions, and an additional source of liquefied organic contaminants.
Another example of a wastewater treatment method is described in U.S. Pat. No. 5,545,327 (Volland). The method uses a treatment tank that contains a series of spaced apart vertical corrugated sheets. The corrugations on each sheet are aligned to define a pathway for the influent to circulate while creating turbulence and mixing. An aerator system is located in the tank to aerate and circulate the wastewater. The circulation of the wastewater and air results in biological growth on the sheets. The growing biomass that forms on the surface of the sheets is displaced by the turbulence of the wastewater, further some of the microbes developing are killed by the shear stresses surrounding the air bubbles. Solid particles formed by these or other causes will settle at the bottom of the tank. Subsequent removal and disposal of the solid particles is therefore required. This system does not provide a configuration that allows for a long retention time of oxygen in the tank because the vertical sheets define vertical pathways through which the oxygen can easily move.
A further example of a wastewater treatment system is described in U.S. Pat. No. 6,153,094 (Jowett et al.). The system is used with septic tank effluent and utilizes a series of polyurethane foam blocks located in a module over which the effluent is passed. The system also includes an air ventilation means located inside the module to sustain the aerobic activity. The foam blocks are of a configuration that creates a series of spaces between the blocks from which water is drained and through which air can subsequently circulate. This system requires an additional air ventilation unit within the tank which can add cost and increase the size of the system.
The above systems and methods either produce excess sludge that subsequently needs to be disposed of, require relatively large volume or require additional components to be added to the system in order to maintain the required operating conditions, such as internal air ventilation systems.
It is therefore desirable to provide a system that overcomes the limitations discussed above.
The present invention provides a wastewater treatment apparatus comprising a treatment vessel having an upper and a lower region, the lower region having an inlet for receiving wastewater to be treated and the upper region having an outlet through which treated wastewater is removed. The vessel includes a plurality of horizontally stacked absorbent baffles arranged so as to allow the wastewater to flow from the inlet to the outlet. Each of the baffles is operable to absorb water, trap and absorb air and solids from the wastewater as it flows from the inlet to the outlet
The present invention further provides a method for treating wastewater that includes the steps of aerating the wastewater, the passing the aerated wastewater upwardly through a treatment vessel that includes a plurality of horizontally stacked baffles adapted to absorb water, trap and absorb air and solids from the wastewater, and then collecting the treated wastewater.